Apparatus for providing a statistical count of particulate material in a fluid

ABSTRACT

An apparatus is provided for counting the average number and size of particulate material contained within a sample volume of a fluid within a transparent bottle without disturbing or breaking the seal, if any, on the bottle. To take a statistical count, a bottle to be inspected is gently shaken to suspend any particulate material therein. Following this operation, the particulate material continues to drift and move about within the bottle for a considerable period of time. A preferred embodiment of the apparatus of the invention makes use of this situation to scan a predetermined volume of fluid within the bottle with a well-defined beam of light by scanning a beam of light over and over a path within a confined area within the fluid for a selected interval of time, i.e., since the particulate material moves and drifts about, scanning over and over the same path is equivalent to scanning different elemental volumes of the fluid. Bursts of scattered light from particulate material illuminated by the beam within a defined region of the fluid along the beam of light are then optically collected, electronically detected, analyzed and counted when certain criteria are met during the selected interval of time. To provide a better statistical average, a larger volume may be scanned by scanning the beam over the path for a longer period of time and averaging the count to provide the count per unit volume.

United States Patent [191 Ogle Jan. 7, 1975 4] APPARATUS FOR PROVIDING A STATISTICAL COUNT OF PARTICULATE MATERIAL IN A FLUID [75] Inventor: Hugh Malcolm Ogle, Palo Alto,

Calif.

[ 1 Assigneei PQLQEFQH,A. Q a SL lelo A to Calif.

22 Filed: July 5,1973

21 Appl. No.: 376,281

[52] US. Cl 356/102, 356/197, 356/207, 356/208, 250/564 [51] Int. Cl. ..G01n 15/00 [58] Field of Search 356/197, 36, 39, 102, 207, 356/208; 250/564 Primary Examiner-William L. Sikes Assistant Examiner-Paul K. Godwin Attorney, Agent, or Firm-Robert H. Himes [57] ABSTRACT An apparatus is provided for counting the average number and size of particulate material contained within a sample volume of a fluid within a transparent bottle without disturbing or breaking the seal, if any, on the bottle. To take a statistical count, a bottle to be inspected is gently shaken to suspend any particulate material therein. Following this operation, the particulate material continues to drift and move about within the bottle for a considerable period of time. A preferred embodiment of the apparatus of the invention makes use of this situation to scan a predetermined volume of fluid within the bottle with a well-defined beam of light by scanning a beam of light over and over a path within a confined area within the fluid for a selected interval of time, i.e., since the particulate material moves and drifts about, scanning over and over the same path is equivalent to scanning different elemental volumes of the fluid. Bursts of scattered light from particulate material illuminated by the beam within a defined region of the fluid along the beam of light are then optically collected, electronically detected, analyzed and counted when certain criteria are met during the selected interval of time. To provide a better statistical average, a larger volume may be scanned by scanning the beam over the path for a longer period of time and averaging the count to provide the count per unit volume.

14 Claims, 9 Drawing Figures Neutral Density Filter PATENTEDJA" H918 3,858,851

SHEET NF 4 I P104 I05 IOI I I -IO| l f I00 I I 7 I00 I r IOI Output Gate 9E5 loz Oufpuf Fig. 6.

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Size of Particulate Material Mlcrons Threshold Level I I0 10* 4o APPARATUS FOR PROVIDING A STATISTICAL COUNT OF PARTICULATE MATERIAL IN A FLUID BACKGROUND OF THE INVENTION Contemporary particulate counters are generally not capable of counting particulate matter inside a sealed bottle, nor can they count with the speed of the apparatus of the present invention. Present techniques using contemporary counters require that the solution to be sampled must be withdrawn from the sample ocntainer and inserted into a special sampling tube supplied with the equipment. Even the best of sterile techniques cannot guarantee that the solution remain free of particulates introduced after the sample solution is removed from its original container; thus in some cases giving erroneous date as to the exact particulate count in the original container. In addition, these methods typically involve filtering a known volume of the sample and counting the particulate material with a microscope. A single reading presently requires a chemical technician for periods up to one hour.

SUMMARY OF THE INVENTION In accordance with the present invention, a laser is utilized to provide a well-defined beam of light which is brought to a focus within a bottle of fluid to be inspected. In a preferred embodiment, this beam of light is rotated about a circular path by passing it though an optical flat that is tilted relative to the path of the beam and rotated about an axis parallel thereto. After passing through the bottle being inspected, the beam is terminated on an opaque target. An optical system surrounding the target, however, is designed to have a comparatively sharp depth of focus for a predetermined segment of the rotating beam within the bottle being inspected. This optical system focuses bursts of scattered light from particulate material illuminated by the beam, which emanate at an acute angle to the beam onto a photo diode. The photo diode converts the light impulses into electrical signals which are then electronically analyzed, both as to amplitude and width, to determine the minimum size and position of the illuminated particulate material along the beam, respectively. Electrical pulses corresponding to particulate material greater than a selected minimum size within the interval defined by the depth of focus of the lens system are counted for an interval of time necessary to scan the desired sample volume. Although the device of the present invention can be calibrated with a known solution to provide the interval of time to scan a selected sample volume, the sample volume is generally equal to the depth of focus of the lens system times the average width of the beam within this interval, times the distance the beam is scanned. Since the beam is scanned at a known velocity, the time required to scan the sample volume can be approximated. Although a circular path has been described, the beam can be scanned over a spiral, flat-helical or other path.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic block diagram of the optical system of the present invention;

FIG. la is a cross-sectional view of section AA of FIG. 1;

FIG. 2 shows an alternate collection lens system for the apparatus of FIG. 1;

LII

FIG. 3 is a schematic block diagram of the electronic analyzing and counting circuitry of the present inventron;

FIG. 4 illustrates voltage waveforms associated with the high gain comparator differential operational amplifier in the apparatus of FIG. 3;

FIG. 5 illustrates a schematic block diagram of the timing apparatus of FIG. 3;

FIG. 6 illustrates voltage waveforms associated with the timing apparatus of FIG. 5;

FIG. 7 shows a typical calibration curve for the apparatus of FIGS. 1 and 3; and

FIG. 8 shows apparatus for off-setting the direction of a beam of light twice and for rotating each off-set at different angular velocities.

DESCRIPTION Referring now to FIG. 1 of the drawings, there is shown a cross-sectional schematic diagram of the optical system of the apparatus of the present invention. More particularly, a laser 10 generates a well-defined beam of light directed along a path 11. A helium-neon laser of the type designated ML-61l has been found to be satisfactory and generates a beam of light of the order of2 mm. in diameter. A condensing lens 12 is disposed in the path 11 of the beam of light and ultimately reduces its diameter to microns. The lens 12 di rects the beam of light along a path parallel to a center line 13 of a cylinder 14 which has a gear 15 attached to the outer periphery thereof that is adapted to be retated by a gear train 16, as shown in FIG. 1A, which is driven by a synchronous motor 17. An optical flat 18 disposed within the cylinder 14 at an angle of the order of 45to the center-line 13. The optical flat 18 may, for example, be composed of a lead glass such as crown glass, in which case it would be made approximately 0.125 inches thick. The optical flat 18 serves to offset the beam oflight from the center-line 13 of the cylinder 14. Thus, when cylinder 14 is rotated by the synchronous motor 17 at a rate of the order of one revolution per second, the angle of the offset: rotates at this angular velocity about the center-line 13, thereby causing the beam of light to be scanned along a circular path that is symmetrically disposed about center-line 13.

The optical-flat 18 may, under certain circumstances, cause some of the beam of light to undergo a double reflection which would cause this light to be scanned around a larger concentric circle than that of the main beam. This portion of the beam of light is intercepted by an opaque plate 20 disposed transversely across the center-line 13 at the exit extremity of cylinder l4 and has a circular aperture 21 that is concentrically disposed about the center line: 13 and has a diameter large enough to allow the main beam of light reflected only once by the optical flat 18 to pass through but sufficiently small to intercept any portion of the beam reflected more than one time. The beam of light that emanates from the aperture 21 of plate 20 is brought to a focus inside a transparent bottle 23 by means of a relay lens 24 disposed adjacent the opaque plate 20. The focal lengths of condensing lens 12 and relay lens 24 are a function of the distance over which the beam of light travels, with the beam of light being brought to a focus within the bottle 23. The transparent bottle 23 contains the fluid to be inspected and is placed up against a stop 25 so as always to be in the right location. A glass plate 26 is disposed in a vertical position, as shown in the drawing, on the side of the bottle 23 opposite from that entered by the beam of light and supports a circular opaque target 27 disposed concentrically about the center-line 13 of the cylinder 14 that is of sufficient diameter to intercept the scanned beam of light.

In passing through the fluid within the bottle 23, the scanned beam of light illuminates particulate material drifting around in the fluid. When thus illuminated, light scatters from the illuminated particulate material in primarily a forward direction, i.e., towards the opaque target 27, but at an acute angle with the beam direction, as illustrated by the dashed lines 30. A collection lens 32 having a short depth of focus that is entirely within the bottle 23 is disposed on the side of support plate 26 opposite from the opaque target 27 concentrically about center-line 13 of cylinder 14. Collection lens 32 is of sufficient diameter as to be able to focus scattered light from illuminated particulate material that by-passes opaque target 27 that is incident thereon onto a silicon photo diode 34, which may, for example, be of a type designated SGD-lOOA. When a single collection lens 32 is used, it may be a convex lens, in which case it is disposed midway between the silicon photo diode 34 and the average depth of focus within the bottle 23 with the focal length, f thereof equal to one-half the distance between the lens 32 and photo diode 34. The depth of focus is controlled by reducing the aforementioned spacing so that f is correspondingly small. Lastly, if it is desired to reduce the intensity of the illumination produced by the laser to increase the range of the electronic circuitry, a neutral density filter 35 may be placed in the path of the beam of light before it enters the bottle 23. Thus, the neutral density filter 35 may be placed between the relay lens 24 and the bottle 23. The filter 35 is shown in dashed lines, as it is used only when comparatively large particulate material is encountered.

Referring to FIG. 2, there is shown an alternate collection lens system 36. Alternate collection lens system 36 includes convex lenses 37, 38 of focal lengths f f respectively, which are of sufficient diameter to intercept scattered light from particulate material illuminated by the beam from laser 10, and are disposed concentrically about the center line 13 from cylinder 14. In addition, lens system 36 includes smaller lenses 39, 40 of focal lengths f f respectively, disposed concentrically about the center line from cylinder 14 intermediate the lens 38 and the photo diode 34. The lenses 37, 38, 39, 40 are placed so that the focal length f,, of lens 37 extends to a point along the desired depth of focus within the bottle 23; the sum of the focal lengths f and f, equals the distance between the lenses 38 and 39; and the focal length f of lens 40 equals the spacing between lens 40 and the photo diode 34. The distances between lens 37, 38 and between lenses 39,40 are not critical and so may be varied to achieve the aforementioned requirements. By using the four lenses 37-40, sharper images may be projected on the photo diode 34 with less optical distortion, while maintaining more control over the depth of focus of these images within the bottle 23. In operation, the lens 37 projects scattered light from within the depth of focus in a collimated beam towards the lens 38. Lens 38, in turn, crosses over the image thus received onto the smaller lens 39, which, in turn, projects the image in a collimated beam towards the lens 40. The lens 40 then focuses the light from the illuminated particulate material onto the photo diode 34.

Referring to FIG. 3, there is illustrated a schematic block diagram of the electronic apparatus for detecting, analyzing, and counting the bursts of light scattered by the illuminated particulate material within the bottle 23. In particular, silicon photo diode 34 is connected to a preamplifier 42 which is, in turn, capacitively coupled through a capacitor 43, to a band pass amplifier 44. Band pass amplifier 44 is designed to pass a band of frequencies from 200 to 100,000 Hertz. The output of bandpass amplifier 44 is connected across a potentiometer 45 which is referenced to ground and has an adjustable output 46 connected to an input A of a high-grain comparator differential operational amplifier 47. A remaining input B is connected to the adjustable tap 48 of a potentiometer 49 which is connected between the positive terminal of an adjustable direct current source of potential 50 and ground, the source of potential 50 also being referenced to ground. The source of potential 50 provides a voltage such as, for example, +10 volts, which is representative of the intensity of the beam of light generated by laser 10. Should the intensity of the beam of light generated by laser 10 change, it is desirable that the potential provided by direct current source 50 be changed accordingly. The adjustable tap 48 of potentiometer 49 is set to provide a threshold voltage to enable the determination of the size of particulate material illuminated by the beam in a manner hereinafter explained.

The high grain comparator differential operational amplifier 47 operates in a manner such that an output voltage, V,,, equal to, for example, +14 volts, is generated when the threshold voltage at input B is of a higher positive magnitude than the voltage at input A from the tap 46 of potentiometer 45 connected across the output of band pass amplifier 44. Alternatively, when the voltage at input A is greater than the threshold voltage at input B, the high gain comparator differential operational amplifier 47 produces an output voltage, V,,, equal to l4 volts.

The output, V from high gain comparator differential operational amplifier 47 is applied to a timer apparatus 51 which passes only pulses of a time duration less than, for example, 20 microseconds, to the output terminal thereof. The operation of the timer apparatus 51 is explained in more detail in connection with FIG. 5 of the drawings.

Returning to FIG. 3, the output of timer apparatus 51 is passed through a normally closed gate 52 to the input of a divide-by-ten counter 54. The passage of signals to normally closed gate 52 is controlled by an output from a l5-second one-shot multivibrator 55, the set input 56 of which is energized by the application of a voltage from a battery 57 through a manually operated switch 58.

The divide-by-ten counter 54 includes a four-stage counter 60 having set and reset inputs 61, 62, respectively, and a lO-count output lead 63. The output from normally-closed gate 52 is connected to the set input 61 of the four-stage counter 54 in parallel with an input to a two-input and gate 64. The l0-count output lead 63 from four-stage counter 60 is connected to the remaining input of and gate 64. An and gate is defined as a gate which produces an information level output when both inputs are at information level. When either one of the inputs are at zero level, there is no output from the and gate. The output from and gate 64 is connected to the set input of a counter 70 and, in addition, is connected back to the reset input 62 of the four-stage counter 60. The four-stage counter 60 produces a count output pulse after receiving 10 pulses applied to the set input 61 thereof. This pulse is applied, together with the tenth pulse applied to the set input 61 thereof, to the inputs of the and gate 64 to produce a pulse at the output thereof. This output pulse is applied back to the reset input 62 of four-stage counter 60 to cause it to start counting again from zero. Thus, the number of pulses applied to the set input 61 is divided by 10. These pulses are, in turn, counted by counter 70. A reset input to counter 70 is connected over a lead 71 to the set input 56 of the second one-shot multivibrator 55. Thus, when multivibrator 55 is energized, causing the normally closed gate 52 to remain open for 15 seconds, the counter 70 is reset to zero, thereby providing a fresh count. The output of counter 70 is applied to a visual readout device 72 to make the infor' mation in counter 70 available. The time of the 15 second one-shot multivibrator 55 is selected on the basis of the time required for the beam to scan the sample volume being analyzed.

Referring to FIG. 4, there is illustrated the manner in which the high gain comparator differential operational amplifier 47 operates. Waveform 80 illustrates a possible waveform appearing at the adjustable tap 46 of potentiometer 45 connected across the output of bandpass amplifier 44. Waveform 80 includes a pulse 81 of an amplitude less than that of the threshold voltage at input B of operational amplifier 47; a pulse 82 of an amplitude greater than the threshold voltage at input B; of and a pulse 83 of an amplitude greater than the threshold voltage, and, in addition, greater than microseconds in width. Waveform 85 illustrates the output voltage, V generated by the operational amplifier 47 in response to the input pulses 81, 82, and 83 of voltage waveform 80. Since pulse 81 does not exceed the threshold voltage at input B of operational amplifier 47, there is no change in the output voltage whereby a constant voltage of +1 4 volts continues to be generated. Upon the occurrence of pulse 82, the threshold voltage at input B is exceeded, causing the output voltage, V to swing to l4 volts for the duration of the pulse 82. Upon the completion of pulse 82, the output voltage, V,,, swings back to +14 volts and remains there until the occurrence of pulse 83. The threshold voltage at input B is again exceeded, causing the output voltage, V to again swing to 14 volts and remain there for the duration of pulse 83, even though it is greater than 20 microseconds. Upon completion of the pulse 83, the output voltage, V,,, again returns to +14 volts and will remain there until such time as the threshold voltage is again exceeded.

Referring to FIG. 5, there is illustrated a schematic block diagram of timer apparatus 51. The timer apparatus 51 includes a 20 microsecond one-shot mutivibrator 90 having a set input which is connected to the input 91 of the timer apparatus 51. The output of the 20 microsecond one-shot multivibrator 90 is connected through a differentiating circuit 92 and a normallyopen gate 93 to the set input of a 20 microsecond oneshot multivibrator 94, the output from which constitutes the output from timer apparatus 51. In addition to the foregoing, the input 91 of the timer apparatus 51 is connected to the control input of the normally open gate 93. Thus, the normally-open gate 93 is closed for the duration of any input pulse applied at input 91 and to the set input of the 20 microsecond one-shot multivibrator 90. The differentiating circuit 92 includes, for example, a 0.00] microfarad capacitor 96 having an output connected through a 1,000 ohm resistor 97 to ground, thereby providing a time constant equal to l microsecond. The voltage generated across resistor 97 constitutes the output of the differentiating circuit 92 and is applied to the input of the normally-open gate 93. Thus, any pulse 98 applied to the input 91 of timer apparatus 51 sets the input of the one-shot multivibra' tor and, at the same time, closes the normally-open gate 93 for the duration of its width. The setting of the input of the one-shot multivibrator 90 generates a pulse 99 having a width of 20 microseconds at the output thereof. The pulse 99 is selected to have a negative excursion, so that the trailing edge has a positive excursion. Since the time constant of the differentiating circuit 92 is only 1 microsecond, the leading and trailing edges of the pulse 99 are differentiated into a negative spike 100 and a positive spike 101 ocurring 20 micro seconds later. Thus, if the input pulse 98 has a duration longer than 20 microseconds, the normally open gate 93 will be closed upon the occurrence of the positive spike 101, whereby nothing appears at the output thereof and the oneshot multivibrator 94 is not set, and nothing appears at the output of timer apparatus 51. On the other hand, if input pulse 98 has a duration shorter than 20 microseconds, the normally open gate 93 opens prior to the occurrence of the trailing edge spike 101, whereby the spike 101 progresses through the normally open gate 93 to the set input of the oneshot multivibrator 94, producing a pulse 102 at the output thereof and, consequently, at the output of timer apparatus 51.

Referring to FIG. 6, there is summarized the operation of timer apparatus 51. When a pulse 104 having a duration longer than 20 microseconds is applied to the input 91 of timer apparatus 51, the pulse 99 at the output of one-shot multivibrator 90, as well as the spikes 100, 101 are generated, while the pulse 104 maintains the normally-open gate 93 in a closed status. Thus, nothing is applied to the set input of the one-shot multivibrator 94 and, consequently, nothing appears at the output of timer apparatus 51. On the other hand, if a pulse 105 of a duration shorter than 20 microseconds is applied to the input 91 of timer apparatus 51, the trailing edge of the pulse 99 generated by the one-shot multivibrator 90, together with the spike 101 occur after the end of the pulse 105. Thus, the normally-open gate 93 is in the open position when the spike 101 oc curs. The spike 101 is thus allowed to proceed through the normally open gate 93 and set the 20 microsecond one-shot multivibrator 94, thus producing the 20 microsecond pulse 102 at the output of timer apparatus 51.

The operation of the particulate material inspection apparatus may be summarized as follows. The laser produces a well-defined beam of light which is focused along the center line of the cylinder 14 by the condensing lens 12. The optical flat 18 disposed at an angle with the center line of cylinder 14 produces an off-set in the beam of light from the laser 10. This offset is rotated by the synchronous motor 17, which rotates the cylinder 14, causing the beam of light to be scanned along a circular path. The scanned beam of light is focussed within a bottle 23 to be inspected and impinges upon an opaque target 27 at the opposite side thereof. Upon being scanned through the liquid, the beam of light illuminates particulate material drifting within the liquid therein, causing light to be scattered at an angle from the path. This scattered light is collected by the collection lens 32 or the alternate collection lens system 36 and focussed on a silicon photo diode 34. In general, an image of particulate material which is in focus on the silicon photo diode 34 generates a sharp pulse less than 20 microseconds in width, depending upon the speed at which the beam of light is scanned. If the image of particulate material is out of focus, i.e., is outside of the depth of focus of the collection lens 32, or the alternate collection lens system 36, the corresponding burst of light is broader, causing an electrical pulse wider than 20 microseconds to be produced by the silicon photo diode 34. Also, if there is a partial hit by the beam of light on a particle of material, a very short burst of light will be produced, which produces a very narrow spike at the output of silicon photo diode 34. In addition to the foregoing, background light illuminated by 60-cycle power may cause l20-cycle light to be reflected by the particulate material.

Referring now to FIG. 3, the preamplifier 40 amplifies all of the signals generated by the silicon photo diode 34. Any direct current is intercepted by the coupling capacitor 43. Thus, if there is a constant illumination of the silicon photo diode 34, the resulting output of this constant illumination will be stopped by the capacitor 43 with the remaining signals applied to the input of bandpass amplifier 44. Background reflections from particulate material occur at I20 cycles because of the typical l20-second alternations per second of the energizing source. These signals are stopped by the low end of bandpass amplifier 44. Spikes produced by partial hits on particulate material, on the other hand, require a higher frequency to pass through and, conse quently, are stopped by the high end of bandpass amplifier 44. The remaining pulses generated by light scattered from particulate material within the fluid of the bottle 23 are applied across the potentiometer 45. The setting of tap 46 of potentiometer 45 is intended as a calibration for the preamplifier 42 and band-pass amplifier 44 and is not normally changed after being adjusted. The adjustable tap 48 of potentiometer 49, on the other hand, selects the threshold level which determines the minimum size particulate material which will be detected.

Referring to FIG. 7, there is shown a representative calibration curve 110 which gives, in microns, a characteristic of the minimum size particulate material desired to be detected versus the threshold level setting. Characteristics of this type are developed by using solutions wherein the particulate material has a known size. Dashed line characteristic 112 illustrates the size of particulate material versus threshold setting with the neutral density filter 35, FIG. I, in place. As is evident from the characteristic 112, the minimum size of the particulate material detected is substantially larger than indicated by the characteristic 110 for the same threshold setting.

The operational amplifier 47 generates pulses in the manner previously explained for each pulse exceeding the threshold voltage at input B thereof. Timer apparatus 51 eliminates any of these pulses exceeding 20 microseconds in width. Energization of one-shot multivibrator opens gate 52 for a predetermined interval and resets counter 70. In the apparatus described, the divide-by-ten counter 54 counts only one pulse in 10 and the time gate 52 is held open, allowing the 10 times the sample volume of fluid to be scanned. The visual readout device 72 provides a visual indication of the count by counter 70. The figures selected are for the purpose of illustration and may vary with the circumstances such as the speed of scan.

Circumstances may also arise where the viscosity of a liquid being inspected prevents particulate material from drifting about, thereby preventing an accurate statistical average of a count of particulate material from being obtained by scanning over the same path. Thus, it may be desirable to scan the well-defined beam of light over an entire confined area. An apparatus for achieving this function is illustrated in FIG. 8. As before, the synchronous motor 17 through drive chain 16 and gear 15 rotates cylinder 14 wherein optical flat I8 is mounted at an angle with the axis of rotation of cylinder 14. In addition, a second cylinder 113 is mounted on the same axis of rotation with an optical flat 114 disposed therein at an angle with the axis of rotation. The optical flat 114 need not be identical in thickness to the optical flat 18. The synchronous motor 17 is coupled to the cylinder 113 through a gear chain 116 and peripheral gear 117 disposed thereabout having a different reduction ratio than the gear chain 16, so that the cylinder 113 rotates at a different angular velocity. When the angular velocity of cylinder 14 is nearly equal to that of cylinder 113, the beam of light scans successive expanding and contracting spirals so as to fill in an entire confined area. Alternatively, when cylinder 1 13 rotates at a substantially faster angular velocity than that of cylinder 14, the beam of light is made to scan a flat-helical path around the axis of the cylinders 14, 113. The beam of light may also be periodically interrupted to prevent over-laps or for other reasons, or may be off-set any plurality of times.

What is claimed is:

1. A liquid inspection apparatus adapted to provide a measure of particulate material in a sample volume, said particulate material being suspended in a liquid contained within a sealed transparent container. said liquid inspection apparatus comprising:

a. means for generating a well-defined beam of light;

b. means for directing said well-defined beam of light through said container;

c. means for scanning said beam of light over no less than one path located entirely within a confined area transverse to the direction of said beam of light, thereby to sequentially illuminate particulate material in the portion of said liquid traversed by said beam whereby bursts of light are scattered therefrom;

(1. means for detecting bursts of light scattered from particulate material along a selected portion of said beam within said container thereby to produce a sequence of electrical signals; and

e. means responsive to said electrical signals occurring within a selected interval of time for providing a measure of particulate material within said sample volume.

2. A liquid inspection apparatus adapted to provide a measure of particulate material in a sample volume, said particulate material being suspended in a liquid contained within a sealed transparent container, said liquid inspection apparatus comprising:

a. means for generating a well-defined beam of light;

b. means for directing said well-defined beam of light through said container;

c. means for shifting said beam to successive collimated paths to scan no less than one path located entirely within a confined area transverse to the direction of said beam of light thereby to sequentially illuminate particulate material in the portion of said liquid traversed by said beam whereby bursts of light are scattered therefrom;

d. means disposed within said confined area for intercepting said beam of light after traversing said container;

e. means extending outwards from said means disposed within said confined area on the side thereof farthest from said container for detecting bursts of light scattered from particulate material along a selected portion of the path of said beam within said container, thereby to produce a sequence of electrical signals; and means responsive to said electrical signals occurring within a selected interval of time for providing a measure of particulate material within said sample volume.

3. In the liquid inspection apparatus as defined in claim 2 wherein said means extending outwards from said means disposed within said confined area on the side thereof farthest from said container for detecting bursts of light scattered from particulate material along a selected portion of the path of said beam within said container includes a convex lens of an area greater than said confined area and of a focal length fdisposed a dis tance Zffrom a point within said selected portion of the path of said beam along an extension of said collimated path thereof, and a photo diode disposed a distance 2f from said lens along the axis of rotation thereof on the side thereof farthest from said container.

4. In the liquid inspection apparatus as defined in claim 2 wherein said means extending outwards from said means disposed within said confined area on the side thereof farthest from said container for detecting bursts of light scattered from particulate material along a selected portion of the path of said beam within said container includes a first convex lens of an area greater than said confined area and ofa focal lengthf, disposed a distance f, from a point within said selected portion of the path of said beam along an extension of said collimated path thereof, a second convex lens of said area greater than said confined area and of a focal length f disposed concentrically about and along the axis of rotation of said first lens, thereby to produce an image at a distance f therefrom, a photo diode disposed along said axis of rotation of said first lens, and third and fourth convex lenses of focal length f and f respectively, disposed intermediate said second convex lens and said photo diode, said second and third lenses being spaced a distance f and f apart and said fourth lens being spaced a distance f from said photo diode.

5. In the liquid inspection apparatus as defined in claim 2 wherein said means extending outwards from said means disposed within said confined area on the side thereof farthest from said container for detecting bursts of light scattered from particulate material along a selected portion of the path of said beam within said container includes a first convex lens of an area greater than said confined area and of a focal lengthf, disposed a distance f from a point within said selected portion of the path of said beam along an extension of said collimated path thereof, a second convex lens of said area greater than said confined area and of a focal length f disposed concentrically about and along the axis of rotation of said first lens, thereby to produce an image at a distance f therefrom, a photo diode disposed along said axis of rotation of said first lens, and means disposed intermediate said second convex lens and said photo diode for focussing said image of said photo diode.

6. A liquid inspection apparatus adapted to provide a count of particulate material in a sample volume, said particulate material being suspended and drifting about in a liquid contained within a sealed transparent container, said liquid inspection apparatus comprising:

a. means for generating a well-defined beam of light;

b. means for directing said well-defined beam of light through said container;

c. means disposed on the near side of said container for off-setting the direction of said beam;

d. means for rotating said offset to cause said beam to be directed along successive collimated paths which scan over a circle thereby to sequentially illuminate particulate material in the portion of said liquid traversed by said beam whereby bursts of light are scattered primarily outwards and at an acute angle from the direction of said beam;

e. means for detecting bursts of light scattered from particulate material along a selected portion of the path of said beam within said container thereby to produce a sequence of electrical signals; and means responsive to said electrical signals occurring within a selected interval of time for providing a count of particulate material within said sample volume.

7. The liquid inspection apparatus as defined in claim 6 wherein said means responsive to said electrical signals occurring within a selected interval of time for providing a count of particulate material within said sample volume includes filter means for eliminating erroneous signals generated background. light and electrical signals generated by partial hits of said beam of light on particulate material.

8. The liquid inspection apparatus as defined in claim 6 wherein said means responsive to said electrical signals occurring within a selected interval oftime for providing a count of particulate material within said sample volume includes voltage comparison means for eliminating electrical signals less than a predetermined threshold potential thereby to count only particulate material no less than a size corresponding to said threshold potential.

9. The liquid inspection apparatus as defined in claim 6 wherein said means responsive to said electrical signals occurring within a selected interval of time for pro viding a count of particulate material within said sample volume includes timing apparatus for rejecting electrical signals longer than a predetermined interval of time thereby restricting said electrical signals to those corresponding to bursts of light emanating from said selected portion of the path of said beam within said container.

10. The liquid inspection apparatus as defined in claim 6 wherein said means responsive to said electrical signals occurring within a selected interval of time for providing a count of particulate material within said sample volume wherein said selected interval of time is n times that necessary for said beam of light to scan said sample volume where n is a positive integer thereby providing a larger count of particulate material, and means for dividing said larger count by n thereby to provide an average count for said sample volume.

11. The liquid inspection apparatus as defined in claim 6 wherein said means responsive to said electrical signals occurring within a selected interval of time for providing a count of particulate material within said sample volume wherein said means for rotating said off-set to cause said beam to be directed along successive collimated paths which scan over a circle constitutes an optical flat disposed at an angle through the path of said beam, and means for rotating said optical flat about an axis parallel to the path of said beam.

12. A liquid inspection apparatus adapted to provide a count of particulate material in a sample volume, said particulate material being suspended in a liquid contained within a sealed transparent container, said liquid inspection apparatus comprising:

a. means for generating a well-defined beam of light;

b. means for directing said well-defined beam of light through said container;

c. means disposed along the path of said beam prior to the entry of said beam with said container for successively off-setting said beam first and second times by the distances greater than zero;

d. means for rotating said first and second off-set at unequal angular velocities to cause said beam to be directed along successive collimated paths which scan over a circular area thereby to sequentially illuminate particulate material in the portion of said liquid transversed by said beam whereby bursts of light are scattered primarily outwards and at an acute angle from the direction of said beam;

e. means for detecting bursts of light scattered from particulate material along a selected portion of the path of said beam within said container thereby to produce a sequence of electrical signals; and

f. means responsive to said electrical signals occurring within a selected interval of time for providing a count of particulate material within said sample volume.

13. The means for rotating said first and second offset at unequal angular velocities as defined in claim 12 wherein the angular rotation of said first off-set is substantially equal to the angular rotation of said second off-set thereby to cause said beam to scan over a spiral path within said circular area.

14. The means for rotating said first and second offset at unequal angular velocities as defined in claim 12 wherein the angular rotation of said first off-set is substantially faster than the angular rotation of said second off-set thereby to cause said beam to scan over a flat helical path within said circular area.

=l l= l =l 

1. A liquid inspection apparatus adapted to provide a measure of particulate material in a sample volume, said particulate material being suspended in a liquid contained within a sealed transparent container, said liquid inspection apparatus comprising: a. means for generating a well-defined beam of light; b. means for directing said well-defined beam of light through said container; c. means for scanning said beam of light over no less than one path located entirely within a confined area transverse to the direction of said beam of light, thereby to sequentially illuminate particulate material in the portion of said liquid traversed by said beam whereby bursts of light are scattered therefrom; d. means for detecting bursts of light scattered from particulate material along a selected portion of said beam within said container thereby to produce a sequence of electrical signals; and e. means responsive to said electrical signals occurring within a selected interval of time for providing a measure of particulate material within said sample volume.
 2. A liquid inspection apparatus adapted to provide a measure of particulate material in a sample volume, said particulate material being suspended in a liquid contained within a sealed transparent container, said liquid inspection apparatus comprising: a. means for generating a well-defined beam of light; b. means for directing said well-defined beam of light through said container; c. means for shifting said beam to successive collimated paths to scan no less than one path located entirely within a confined area transverse to the direction of said beam of light thereby to sequentially illuminate particulate material in the portion of said liquid traversed by said beam whereby bursts of light are scattered therefrom; d. means disposed within said confined area for intercepting said beam of light after traversing said container; e. means extending outwards from said means disposed within said confined area on the side thereof farthest from said container for detecting bursts of light scattered from particulate material along a selected portion of the path of said beam within said container, thereby to produce a sequence of electrical signals; and f. means responsive to said electrical signals occurring within a selected interval of time for providing a measure of particulate material within said sample volume.
 3. In the liquid inspection apparatus as defined in claim 2 wherein said means extending outwards from said means disposed within said confined area on the side thereof farthest from said container for detecting bursts of light scattered from particulate material along a selected portion of the path of said beam within said container includes a convex lens of an area greater than said confined area and of a focal length f disposed a distance 2f from a point within said selected portion of the path of said beam along an extension of said collimated path thereof, and a photo diode disposed a distance 2f from said lens along the axis of rotation thereof on the side thereof farthest from said container.
 4. In the liquid inspection apparatus as defined in claim 2 wherein said means extending outwards from said means disposed within said confined area on the side thereof farthest from said container for detecting bursts of light scattered from particulate material along a selected portion of the path of said beam within said container includes a first convex lens of an area greater than said confined area and of a focal length f, disposed a distance f1 from a point within said selected portion of the path of said beam along an extension of said collimated path thereof, a second convex lens of said area greater than said confined area and of a focal length f2 disposed concentrically about and along the axis of rotation of said first lens, thereby to produce an image at a distance f2 therefrom, a photo diode disposed along said axis of rotation of said first lens, and third and fourth convex lenses of focal length f3 and f4, respectively, disposed intermediate said second convex lens and said photo diode, said second and third lenses being spaced a distance f2 and f3 apart and said fourth lens being spaced a distance f4 from said photo diode.
 5. In the liquid inspection apparatus as defined in claim 2 wherein said means extending outwards from said means disposed within said confined area on the side thereof farthest from said container for detecting bursts of light scattered from particulate material along a selected portion of the path of said beam within said container includes a first convex lens of an area greater than said confined area and of a focal length f, disposed a distance f1 from a point within said selected portion of the path of said beam along an extension of said collimated path thereof, a second convex lens of said area greater than said confined area and of a focal length f2 disposed concentrically about and along the axis of rotation of said first lens, thereby to produce an image at a distance f2 therefrom, a photo diode disposed along said axis of rotation of said first lens, and means disposed intermediate said second convex lens and said photo diode for focussing said image of said photo diode.
 6. A liquid inspection apparatus adapted to provide a count of particulate material in a sample volume, said particulate material being suspended and drifting about in a liquid contained within a sealed transparent container, said liquid inspection apparatus comprising: a. means for generating a well-defined beam of light; b. means for directing said well-defined beam of light through said container; c. means disposed on the near side of said container for off-setting the direction of said beam; d. means for rotating said off-set to cause said beam to be directed along successive collimated paths which scan over a circle thereby to sequentially illuminate particulate material in the portion of said liquid traversed by said beam whereby bursts of light are scattered primarily outwards and at an acute angle from the direction of said beam; e. means for detecting bursts of light scattered from particulate material along a selected portion of the path of said beam within said container thereby to produce a sequence of electrical signals; and f. means responsive to said electrical signals occurring within a selected interval of time for providing a count of particulate material within said sample volume.
 7. The liquid inspection apparatus as defined in claim 6 wherein said means responsive to said electrical signals occurring within a selected interval of time for providing a count of particulate material within said sample volume includes filter means for eliminating erroneous signals generated background light and electrical signals generated by partial hits of said beam of light on particulate material.
 8. The liquid inspection apparatus as defined in claim 6 wherein said means responsive to said electrical signals occurring within a selected interval of time for providing a count of particulate material within said sample volume includes voltage comparison means for eliminating electrical signals less than a predetermined threshold potential thereby to count only particulate material no less than a size corresponding to said threshold potential.
 9. The liquid inspection apparatus as defined in claim 6 wherein said means responsive to said electrical signals occurring within a selected interval of time for providing a count of particulate material within said sample volume includes timing apparatus for rejecting electrical signals longer than a predetermined interval of time thereby restricting said electrical signals to those corresponding to bursts of light emanating from said selected portion of the path of said beam within said container.
 10. The liquid inspection apparatus as defined in claim 6 wherein said means responsive to said electrical signals occurring within a selected interval of time for providing a count of particulate material within said sample volume wherein said selected interval of time is n times that necessary for said beam of light to scan said sample volume where n is a positive integer thereby providing a larger count of particulate material, and means for dividing said larger count by n thereby to provide an average count for said sample volume.
 11. The liquid inspection apparatus as defined in claim 6 wherein said means responsive to said electrical signals occurring within a selected interval of time for providing a count of particulate material within said sample volume wherein said means for rotating said off-set to cause said beam to be directed along successive collimated paths which scan over a circle constitutes an optical flat disposed at an angle through the path of said beam, and means for rotating said optical flat about an axis parallel to the path of said beam.
 12. A liquid inspection apparatus adapted to provide a count of particulate material in a sample volume, said particulate material being suspended in a liquid contained within a sealed transparent container, said liquid inspection apparatus comprising: a. means for generating a well-defined beam of light; b. means for directing said well-defined beam of light through said container; c. means disposed along the path of said beam prior to the entry of said beam with said container for successively off-setting said beam first and second times by the distances greater than zero; d. means for rotating said frist and second off-set at unequal angular velocities to cause said beam to be directed along successive collimated paths which scan over a circular area thereby to sequentially illuminate particulate material in the portion of said liquid transversed by said beam whereby bursts of light are scattered primarily outwards and at an acute angle from the direction of said beam; e. means for detecting bursts of light scattered from particulate material along a selected portion of the path of said beam within said container thereby to produce a sequence of electrical signals; and f. means responsive to said electrical signals occurring within a selected interval of time for providing a count of particulate material within said sample volume.
 13. The means for rotating said first and second off-set at unequal angular velocities as defined in claim 12 wherein the angular rotation of said first off-set is substantially equal to the angular rotation of said second off-set thereby to cause said beam to scan over a spiral path within said circular area.
 14. The means for rotating said first and second off-set at unequal angular velocities as defined in claim 12 wherein the angular rotation of said firSt off-set is substantially faster than the angular rotation of said second off-set thereby to cause said beam to scan over a flat helical path within said circular area. 